No as dangerous as first hand. Common sense will be, first hand smoker already such in all the nicotine, and the body neutralise a bit. So the air he breather out with be a combination of oxygen and carbon dioxide. So the nicotine and tar content, will be diluted. Sometimes it's best to use common sense and a test of experiment, instead of believing a stupid 'mad scientist' who claims that he's right and define common sense. Pwee!